Thus, taking a thorough clinical history is key see below. Medical Education and Consultation Related to Human Parasitic Infections The expansion of medical knowledge in the past decade is incredible. The medical profession has responded through increased specialization and subspecialization. In the past, a surgeon might specialize as an orthopedic surgeon, whereas now, it is common to find practices with individuals who specialize in only knee or hip disease. Therefore, it is unreasonable to expect individuals who are not subspecialty trained in microbiology or infectious diseases to keep abreast of changes in clinical microbiology, one of the fastest-paced fields.
A clinical parasitologist or clinical microbiologist with expertise in parasitology is perfectly positioned to help educate physicians and provide guidance in test selection. These laboratorians, whenever possible, should participate in educating the next generation of physicians, not just to teach them at that point in their career but also to inform them that highly trained laboratorians remain available to assist them as needed throughout their professional careers.
Additionally, this group should participate, whenever possible, in medical technology training programs.
This type of engagement translates into improved patient care. A clinical microbiologist should work with the medical staff to formulate the test requisition forms, which are largely becoming solely electronic. They should work to aid clinicians in finding and using the most appropriate test for the clinical scenario encountered see below.
They should play an active role in monitoring test utilization and use instances of inappropriate utilization as opportunities for education. Importance of a Complete Patient History Physician and Diagnostic Laboratory The importance of location in determining the type of parasite that the patient may have acquired has been noted above and should be disclosed as part of taking a thorough history. The clinical history is designed to discover epidemiologic risk factors that are important for guiding testing.
In addition to general aspects of a history assessment, specific questions concerning past medical history, countries of previous residence, travel, outdoor activities, family, food, and drinking water should be addressed. Specific examples of the importance of each of these follow. Where a patient lives or has lived is important for an assessment of the risk of having acquired parasites in the patient's native country that are not endemic in their current country Cyclospora cases have been reported from the United States, Canada, and the United Kingdom.
It is very common to find evidence of multiple gastrointestinal parasites in the stools of children who have been adopted from a resource-poor country where parasites are highly endemic into a low-prevalence, resource-rich country Although there are no accepted general guidelines in these cases, routine parasitology examinations ova and parasites may be an appropriate option. Travel history similarly discloses potential risks to the traveler Cyclospora , Mexico , as does questioning about specific outdoor activities Cryptosporidium , swimming in late summer, contact with calves.
A history of backpacking and drinking stream water is classically associated with giardiasis, for example. Family history and past medical history are important to disclose inherited genetic diseases or other conditions that may put patients at increased risk for certain parasitic diseases. For example, individuals with common variable immunodeficiency are at increased risk for Giardia lamblia G. Food and drink histories are among the most important, since many parasitic infections are acquired through ingestion. For example, the discovery that a patient is a bear hunter would make one consider trichinellosis, when in the absence of a classical presentation it might otherwise not be considered Laboratory type.
It should be recognized that not all laboratories offer the same types of services. Physician office-based laboratories may offer no parasitology but should have clear guidelines regarding the best test to perform for each clinical scenario and the materials for appropriate specimen collection and shipping. The smallest of these laboratories are usually able to perform moderately complex tests and, if the test volume is sufficient, may consider offering one of the easy-to-use, single-use, lateral-flow enzyme immunoassays EIAs for commonly encountered parasites, such as Giardia lamblia G.
Small hospital laboratories may offer limited parasitology, the degree of which should be determined by test volume and technologist competency. It is important to critically assess competency for very low-volume tests, as it is difficult to remain proficient if testing is not commonly performed. In instances of low-volume testing, it may be better for the patient if the test is referred to a reference laboratory where expertise is maintained.
- Charles Louis Davis and Samuel Wesley Thompson DVM Foundation;
- Gryll Grange.
- Rubbing Salt.
Small hospital laboratories should be able to perform EIAs and pinworm prep examinations, although these are no longer common test requests. The performance of a full ova and parasite examination should be based on skill and competency. Many of the newer multiplex molecular diagnostic assays for gastrointestinal pathogens include some parasite pathogens, such as Giardia lamblia G. These are moderately or highly complex tests and represent options for expanded testing in small laboratories that may lack parasitology expertise.
Large hospital laboratories and reference laboratories should offer full parasitology services.
These include enzyme immunoassays, full ova and parasite examination, modified acid-fast staining for Cryptosporidium , Cyclospora , and Cystoisospora , modified trichrome staining for microsporidian species, and the ability to identify adult helminths that may be passed in the stool. These laboratories will often also offer advanced molecular diagnostics for parasites. These tests may include FDA-approved multiplex assays for a variety of gastrointestinal pathogens or laboratory-developed tests for specific agents e.
Thorough competency assessments are necessary, and participation in challenging parasite proficiency testing should be ongoing.
Nonhuman Primates in Biomedical Research
Test menu complexity. The test menu should include the options available for each clinical scenario that are most commonly encountered. These options are many, and it is likely that a busy clinician may not always review these options thoroughly, which might lead to inappropriate test orders.
Inappropriate orders have several adverse consequences. Foremost among these is the negative impact on patient care. If the clinician selects the wrong test, the diagnosis may be missed.
If the wrong selection is discovered and the correct test is eventually performed, then the diagnosis is delayed and there is waste in performing the initial incorrect test. Ordering many tests is a poor and wasteful practice that should be discouraged. Not only is this costly, but tests that are performed for which there is not a good pretest likelihood i.
Examples of recommendations associated with particular tests are provided Table 1. Test Ordering Options, Monitoring, and Intervention: Patient Clinical Relevance Tests in the clinical parasitology section, with the exception of rapid immunoassays, are manual, are time-consuming, and require personnel expertise. Therefore, to preserve limited resources, these tests should be ordered judiciously. Additionally, some tests may sound alike, without differences clearly delineated. Therefore, it is not surprising that providers may select an inappropriate test.
Test menu design is an area that is often not given due consideration and is therefore responsible for many unnecessary orders. Some laboratories may elect to use a case history form to guide appropriate testing Fig. Example of a case history form that can be used to guide clinician ordering for stool ova and parasite testing. It is also useful to periodically monitor who in the practice is ordering which tests. Order sets decrease the time needed to search for individual tests. Unfortunately, these sets are often wasteful and filled with more tests than are needed. Order sets are not frequently curated and kept current.
There are a number of interventions that can be used to decrease unnecessary orders. Tailoring the order set for the pathogens most likely to be encountered is one approach, while educating clinicians is another option. For example, a key take-home message is that a patient from an area of endemicity or an immunocompromised patient may warrant additional tests.
A number of interventions can be useful in averting unnecessary testing, which includes testing for parasites. One of these is to electronically block same-day duplicate orders, should they occur In both instances, the clinician can override the electronic blockade by contacting the laboratory 2 — 6 , These interventions have diminished the number of orders that have been placed without thoughtful consideration, while still allowing clinicians to order the test if they really believe that it is clinically necessary.
These patients are at risk for more-severe disease caused by commonly encountered agents, as well as disease caused by pathogens less commonly encountered in an immunocompetent host.
Laboratory Diagnosis of Parasites from the Gastrointestinal Tract | Clinical Microbiology Reviews
Therefore, when investigating the cause of a likely infectious diarrheal syndrome in an immunocompromised host, both common and less common agents should be considered 5 , Although a patient is immunocompromised, an epidemiologic exposure history is still important to obtain, as this may disclose the most likely pathogen.
Finally, if the cause remains undetermined, one should consider an assessment of Microsporidia. Although Microsporidia are taxonomically now classified as fungi, most testing remains in the parasitology sections of the laboratory 5. If the morphological assessment for Microsporidia is negative and clinical suspicion remains high, then a PCR analysis should be considered because of its superior sensitivity. Use of Standard Precautions Clinical laboratories should follow the requirements related to standard precautions, which state that all patients and all laboratory specimens are potentially infectious and should be handled accordingly 37 — While the OSHA documents place the emphasis on blood-borne pathogens, such as HIV and hepatitis B and C viruses, standard precautions recognize that all infectious agents and all other potentially infectious material, except sweat, pose a risk to the health care worker Methods include those used to minimize exposure to infectious agents, to shield the laboratory worker from infectious material through a set of engineering and work practice controls, and to use personal protective equipment PPE.
In situations where differentiation between body fluid types is difficult or impossible, all body fluids shall be considered potentially infectious. Also, the OSHA regulations require that employers provide hepatitis B vaccination and postexposure evaluation and follow-up, communicate the hazards to employees, and maintain appropriate records Employees who decline immunization against hepatitis B virus are required to sign a hepatitis B vaccine declination form. Microscope for general use. Good-quality microscopes and light sources are required for the examination of specimens for parasites.
Calibration of the microscope is essential; excellent references are available for training in this method 2 — 7. This flexibility allows the microscope to be used by numerous individuals.
All microscopes should be covered when not in use; this will help keep the instrument clean. Instrument calibration should be performed and documented yearly or more often if the instrument receives heavy use or is moved frequently. It is also mandatory that the lens of any oil immersion objective be cleaned with lens paper after each use. Use several layers and very little pressure to prevent removal of the coatings on external surfaces of the lens. Overall, the centrifuge size and configuration depend on the method being used.
Either a table or floor model centrifuge is acceptable.
A free-swinging or horizontal head is recommended. When routine centrifugation or a fecal concentration is performed, the sediment is deposited evenly on the bottom of the tube. Also, if the sediment surface is flat and the tube cannot be turned upside down which will depend on the viscosity of the sediment , this configuration allows easy removal of the supernatant fluid from the sediment. Many laboratories currently use carrier cups with sealed closures; this feature, in addition to capped centrifuge tubes, will minimize any possible aerosol formation. It is generally recommended that the speed be checked and documented every 6 months or on a yearly basis.
Fume hood. Chemical fume hoods are recommended when there is risk of exposure to hazardous fumes or splashes while chemical solutions are being prepared or dispensed. Chemical fume hoods are certified and documented annually. Some laboratories also use fume hoods to reduce the odors found when fecal specimens are tested. Anything placed in the fume hood for storage reagents, supplies, equipment must not interfere with the proper airflow. BSCs operate at a negative air pressure, air passes through a HEPA filter, and this vertical airflow acts as a protective barrier between the cabinet and the user.
Although a BSC is not required for processing routine specimens in a diagnostic parasitology laboratory, some laboratories use class I open-face or class II laminar-flow BSCs for processing all unpreserved specimens Use of a biological safety cabinet is recommended if the laboratory performs cultures for parasite isolation.